[Line Items] for Income Taxes [Table]

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Net reduction to income tax provision, including the recognition of interest and penalties and offsetting tax assets, if unrecognized tax benefits were recognized.

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Income Tax Expense

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Liability

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Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Transition Tax For Accumulated Foreign Earnings, Provisional Liability, Percentage

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign tax credit carryforwards.

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Amount of deferred tax liability attributable to taxable temporary differences from undistributed earnings of subsidiaries and other recognized entities not within the country of domicile of the entity.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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The amount of income taxes from which a reporting entity is exempt or for which it will receive a reduction in income taxes as a result of the income tax holiday granted by the taxing jurisdiction.

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Per share amount effect of the income tax benefit resulting from the income tax holidays granted by taxing jurisdictions.

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The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

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Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

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Amount of unrecognized tax benefits.

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Amount accrued for interest on an underpayment of income taxes and penalties related to a tax position claimed or expected to be claimed in the tax return.

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Income Taxes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2015
Income Taxes [Line Items]
Blended statutory tax rate		24.53%	35.00%	35.00%
Deferred tax asset, provisional income tax amount		$ 104.4
Transition tax liability for foreign subsidiaries, provisional expense		395.8
Income taxes payable		389.4
Deferred tax liabilities related to foreign withholding taxes on future distributions on historic earnings		22.7	$ 0.0
Deferred tax assets related to U.S. foreign tax credits attributable to the foreign withholding taxes		9.9
Tax benefit attributable to non-U.S. government sponsored tax incentive programs		$ 52.3	$ 43.4	$ 33.9
Tax benefit per diluted share attributable to non-U.S. government sponsored tax incentive programs		$ 0.41	$ 0.33	$ 0.26
Gross unrecognized tax benefits		$ 20.1	$ 31.1	$ 32.4					$ 43.9
Accrued interest and penalties for unrecognized tax benefits		2.5	4.0
Benefits (expense) recognized for interest and penalties related to unrecognized tax benefits		1.5	$ 1.2	$ (0.1)
Reasonably possible amount of reduction of gross unrecognized tax benefit in the next twelve months		6.0
Reasonably possible amount of net reduction to income tax provision in the next twelve months if unrecognized tax benefits were recognized, including the recognition of interest and penalties and offsetting tax assets		5.5
Scenario, Forecast
Income Taxes [Line Items]
Blended statutory tax rate	21.00%
Transition tax liability, percentage due					25.00%	20.00%	15.00%	8.00%
Other current liabilities
Income Taxes [Line Items]
Income taxes payable		31.1
Other liabilities
Income Taxes [Line Items]
Income taxes payable		358.3
Non-United States
Income Taxes [Line Items]
Deferred tax liabilities related to foreign withholding taxes on future distributions on historic earnings		$ 34.8